Touch sensitive function has become an important function of modern electronic devices. Commonly used touch sensitive modules which provide the touch sensitive function include resistive touch screens, capacitive touch screens, and optical touch screens. They have been adopted in a variety of electronic devices in different practical applications.
An optical touch sensitive module detects touched positions on the touch screen by way of optical detectors. No extra pressure needs to be applied onto the screen, but only touching or even approaching close to the screen is enough for the optical detectors to conduct detection. The optical touch sensitive module usually has a plurality of infrared light sources and light detecting units arranged around the module. The infrared light sources are used for emitting infrared light toward an objective space above the screen surface. Once an object is present in the objective space and blocks the infrared light, the resulting optical information can be captured by the light detecting units from different view angles, and then analyzed for obtaining positions and moving traces of the object in the objective space.
However, the cost of the light detecting unit is high, so the total cost of the optical touch sensitive module is high as well. Therefore, how to solve the problem of the high cost and to popularize the optical touch sensitive module is a major subject in this field.